Stabilizer for alternating-current line regulators



March 1949i P. H. ODESSEY 2,436,322

STABILIZER FOR ALTERNATING-CURRENT LINE REGULATORS Filed Feb. 10, 1945 P904 flat-55.5

Patented M11122, 1948 STABILIZER FOR ALTERNATING-CURRENT LINE REGULATORS Paul H. Odcssey. Great Neck, N. Y., assiznor to Raytheon Manufacturing ilompany, Newton, Mass, a corporation of Delaware Application February 10, 1945, Serial No. 577,273

- 7 Elaimo. l

My present invention relates to' A.-C. line regulating systems which include D.-C. operated control means for maintaining substantially constant A.-C. output voltage, and more particularly to means for stabilizing the operation of such control means.

It is known, in regulating an A.-C. line, to connect an impedance, for example, a saturable reactor, in series with the primary of a transformer across the secondary of which a load is connected. and vary the magnetic saturation of said reactor with a 11-0. whose magnitude is a function of the magnitude of the A.-C. output volt age delivered to the load. .In so doing, the impedance of the transformer input is so varied as to counteract any tendency toward fluctuation in the line voltage. I have found, however, that such systems have an appreciable inherent timeconstant, which interferes with their sensitivity and stability, and causes hunting.

It is, therefore, the main object of my present invention to eliminate the disadvantages referred to, and in so doing, provide'a sensitive and stable circuit, which is free of hunting, for controlling an A.-C. line regulator of the general character described.

It is a further object of my present invention to provide a circuit, having the foregoing highly desirable characteristics, which is simple, which is composed of standard parts, and in which the chances of over-voltage conditions, due to failure of any of the components, are maintained at a minimum.

These and other objects and advantages of my present invention, which will become apparent as the detailed description thereof progresses, are attained in the following manner:

A portion 013 the A.-=C. output which is applied to the load is rectified, and the resulting 11-0. is compared with a reference potential establlshed in the system in order to derive a variable D.-C. proportional to the difference therebetween. The variable difference D.-C. thus obtained is utilized to adjust the magnitude of a control 11-0. intended to be applied to the lineregulating element which, as stated, may be a saturable reactor. By way of example, the control D.-C. may be obtained by rectifying another portion of the A.-C. output of the system, or it may be obtained by rectifying it separately regulated A.-C. source. Also by way of example, the magnitude of the control D.-C. may be adjusted by altering the phase of another portion of the A.-C. output of the system as a function of the fluctuation thereof, and utilizing the resulting phase-shifted output to operate the control D.-C. generator. Other means for adjusting the magnitude of the control D.-C. will readily suggest themselves.

In orde to eliminate hunting, a portion of the control D.-C. is applied, preferably, as negative feedback, to the variable difference D.-C. generator so as to oppose and thereby dampen any tendency to sudden changes in the input to said generator.

By these expedients, the disadvantages of known A.-C. regulating systems, to which refer= ence has been made, are eliminated, and a simple system is presented which is sensitive and staple, and therefore affords. good regulation.

In the accompanying specification I shall de scribe, and in the annexed drawing show, an illustrative embodiment of the regulating system of my present invention. It is, however. to be clearly understood that do not wish to be limited to the exact details herein shown and described for purposes of illustration only, mas much as changes therein may be made without the exercise of invention and within the true spirit and scope of the claims hereto appended.

In said drawing, the single figure is a schematic diagram of an A.-C. line regulating system assembled in accordance with the principles of my present invention.

Referring now more in detail to the aforesaid illustrative embodiment of my present invention, and with particular reference to the drawing, the numerals l and i2 designate the conductors of an A.-C. line which it is desired to regulate for the purpose of maintaining substantially con stant output voltage.

Connected across the line, with a saturable reactor 3 shunted by a resistor t in series therewith, is the primary of a transformer 5, preferably, an autotransformer, the secondary of said transformer being connected by conductors t and i to a load 8.

Inasmuch as the impedance of the input circuit to the transformer 5 is an inverse function of the magnetic saturation of the saturable reactor 3,

reactor and thereby increasing the'impedance of the transformer input circuit. and vice versa.

While not limited thereto, I prefer that the source 9 of control D.-C. consist of a rectified portion of the A.-C. output of the system. For example, there may be connected across the load 8. by means of conductors l and i I, the primary i2 of a plate and filament transformer i3, said transformer including a secondary winding l4 t0 the opposite terminals of which are connected, through conductors i5 and i6 and dropping resistors I1 and i8, the anodes l9 and 29 of a pair of grid-controlled gas discharge tubes 2| and 22, known as thyratrons. Said tubes include filaments 23 and 24 which may be heated by current conveyed thereto through parallel pairs of conductors 25 and 26 connected across the secondarv of a filament transformer 21 the primary of which is connected by conductors 28 and 29 across the A.-C. line to be rc"ulated. The filaments of the thyratrons may be connected, through a center-tap on the secondary of the transformer 21 and a conductor 30, to one input terminal of the saturable reactor 3, and the anodes of said thyratrons may be connected, throu h a center-tap on the secondary winding l4 of the transformer i2 and a conductor 3i, to the remaining input terminal of said saturable reactor, whereby, upon exercising appropriate control over the grid potentials of said thyratrons, full-wave rectificationof a portion of the A.-C. output of the system is obtained. If desired. the input circuit to the saturable reactor may include an "Edison" time delay 32, whereby, when the system is first put into operation, no plate potential is applied to the thyratrons until the filaments thereof become appropriately heated.

The magnitude of the D.-C. output of the thyratrons 2i and 22 can be adjusted in a number of ways, but I prefer to accomplish this by controlling the phase relationship between the input to the anodes l9 and and the input to the grids 33 and 34. For this purpose, I provide a phaseshifting network 35 which includes, in series, another secondary winding 38 on the transformer i3, a parallel combination of a. resistor 31 and capacitor 38, and another saturable reactor 39, the output of this network being taken across a voltage divider consisting of resistors 40 and 4i connected by a conductor 42 to one output terminal, and by a conductor 43 to a center-tap on the secondary winding 36, the latter constituting the other output terminal. The junction of the resistors 40 and 4| is connected by a conductor 44 to the center-tap on the secondary of the filament transformer 21, and therethrough, to the filaments 23 and 24 of the thyratrons 2i and 22. The.

grids 33 and 34 of said thyratrons are connected, respectively through current-limiting resistors 45 and 46, to the outer terminals of the resistors 40 and M, whereby the output of the phase-shifting network 35 is differentially applied to said thyratrons.

The phase of the output of the network 35 may be adjusted with respect to the anode input to the rectifying thyratrons by altering the impedance of said network, and this may be accomplished by applying a variable D.-C. to the saturable reactor 39. Such a D.-C. should, of course, vary in magnitude as a function of the magnitude of the A.-C. output of the system, and I derive such a D.-C. in the following manner:

The transformer .l3 may include another secondary winding 41 the outer terminals of which are connected by conductors 48 and 49 to the anodes 50 and BI of a full-wave rectifier tube 52, said tube including an indirectly heated cathode 53 and a heating filament 54. The latter may be connected, as indicated, to still another secondary winding 55 on the transformer i3. The rectified output is obtained across conductors 58 and 51, respectively connected to the cathode 53 and a center-tap on the secondary winding 41, said output being filtered by a series choke 58 and a shunting capacitor 59. A choke-input filter, such as is shown in the drawing, results in regulation in accordance with the average value of the A.-C. output of the system; but it regulation in accordance with the peak value of said output is desired, a capacitor-input filter should be utilized.

In any event, the D.-C. thus obtained is em ployed to control the magnitude of the phase shift introduced by the network 35. I prefer, however, that said D.-C. not be directly fed to the impedance-control element of said network, but instead, that said D.-C. be compared with a reference potential established in the system in order to derive a variable difference D.-C. which, in turn, be applied to the phase-shifting network. I thereby attain smoother and more stable'control.

For this purpose, I connect across the rectified output just described a conventional voltage-regulating gas discharge tube 60, and a current-limiting resistor 6| and potentiometer 62 in series therewith. The tube 60 constitutes an automatically variable impedance and therefore, the drop across the same remains constant regardless of fluctuations in the input thereto, thus establishing a reference potential in the system.

I also connect across the aforementioned rectified output, in shunt with the circuit including the gas-discharge tube 80, a. fixed impedance in the form of a resistor 63, in series with a second gas discharge tube 64 and a potentiometer 65, the junction of said potentiometer and said tube being connected to the adjustable arm 66 of the po tentiometer 62 for a purpose later to be described. It will be noted that variations in the input to the tube 64 result in variations in the drop across the resistor 63, and hence I have provided, at the Junction of said resistor 63 and the gas discharge tube 64, a variable potential for comparison with the reference potential provided by the fixed drop across the gas dischargetube 60. The difference between these potentials is obtained between the Junction of the resistor 63 and tube 64, and the Junction of the resistor 6i and tube 60. The

'variable difference D.-C, thus obtained is applied to a D.-C. amplifier 81, the grid 68 of which is connected, through an input grid resistor 69, to the above-mentionedjunction betweentheresistor 63 and tube 64, and the indirectly heated cathode 10 of which is connected, through a resistor ii to the above-mentioned iunction between the resistor 6i and tube 60. The plate 12 of the amplifier 61 is connected to the positive lead 56 of the rectified output from the tube 52 through the sat urable reactor 39 and a load resistor I3. The grid 68. of the amplifier 61 is maintained at an appropriate potential with respect to the cathode 10 of said tube by adjustment of the arm 66 of the potentiometer 62.

I thus obtain a variable difference D.-C. whose magnitude is proportional to any variations in the A.-C. output of the system, and by utilizing this D.-C. to vary the impedance of the saturable retrons 2| and 22 which is applied to what may be termed the primary control element of the system, namely, the saturable reactor 3.

Now, I find that if the system is utilized as described up to this point, it has a tendency to hunt. and in order to eliminate this tendency, I prefer to proceed in the following manner:

A portion of the control D. C. which is fedto the saturable reactor 3 is applied across a network including a parallel combination of a r'esistor l4 and capacitor 15, and a series resistor 18. The time-constant or the combination of the resistor I4 and the capacitor 15 is long compared to the inherent time-constant or the system, and the voltage thereacross is applied, through a grid resistor TI and the. adjustable arm 18 of the potentiometer 65, between the grid 19 and cathode 8B of another D.-C. amplifier 8i, appropriate bias on the amplifier 8| being obtained by adjusting the position of said arm 18. The plate 82 of the amplifier BI is connected, through a load resistor 83, to the junction of the resistor 63 and gas discharge tube 65, the output across said load resistor being applied as negative feedback, through a coupling capacitor 84, to the input to the variable difierence D.-C. amplifier 5]. The magnitude oi the feedback voltage is a function of the rate of change of the control B. 0. fed to the saturable reactor 3. and there by, there is obtained a tendency to'oppose sudden changes in the magnitude of the A.-C. output of the system, eliminating hunting.

Thiscompietes the description or the aforesaid illustrative embodiment of the line-regulating system of my present invention, and the operation thereof may be briefly summarized as follows:

Assuming that the line voltage tends to rise, the result will be an increased rectified output between the conductors 56 and El, and an increased difference between the variable potential at the junction of the resistor 63 and tube 54, and the fixed reference potential across the tube 60. More current, therefore, passes through the resistor 63, and a negative-going input voltage is applied to the D.-C. amplifier 6i. Current through the saturalole reactor 39 is reduced as a result; the impedance of the network 35 is increased; and the phase angle between the output of said network 35 and the anode input to the thyrathrons 2| and 22 is likewise increased. This results in a drop in the magnitude of the rectified output of said thyratrons, in other words, in the control D. C. applied to the saturable reactor 3. Therefore, the impedance across the conductors l and 2 is increased, and the tendency for the voltage induced in the secondary oi the transformer 5 to rise is counteracted.

An initial drop in the line voltage reverses the direction of the tendencies described above in connection an initial increase in the line voltage.

It will thus be noted from all of the foregoing that I have provided a sensitive, simple, and efficient control circuit for stabilizing A.-C line regulating systems, and rendering said systems free from hunting.

Other advantages of the systems of my present invention will readily occur to those skilled in the art to which the same relate.

What is claimed is:

1. In a circuit for stabilizing the operation of the control means of an A.-C. line regulating system, means for comparing the magnitude of the A.-C. output of said system with a reference potential established therein, and deriving therefrom a variable D, C. proportional to the dinerence therebetweeen, comprising: means for rectifying a portion or said A.-C. output; an automatically variable impedance, receptive oi the output of said rectifying means, and presenting a constant 'v'oltage drop thereacross; a second automatically variable impedance in series with a fixed impedance, connected in shunt with said first automatically variable impedance, likewise receptive offth'e output'o! said rectifying means, and presenting a variable potential, at the Junetion'oi' said series connection, in response to fluctuations in said A.-C. output; and an electronic discharge device having its input connected across the series network including said fixed impedance and said first automatically variable impedance, whereby the diii'erence between said variable potential and said constant voltage drop is applied thereto' and amplified thereby.

2. In a circuit i'or stabilizing the operation of the control'ineans of an A.-C. line regulating systerm, means for comparing the magnitude of the A.-C. output of said system with a reference potential established therein, and deriving therefrom a variable D.-C. proportional to the difference therebetween, comprising: means for rectitying a portion of said A.-C. output; a gas discharge tube, receptive of the output of said rectitying means, and presenting a constant voltage drop thereacross; second gas discharge tube in series with a fixed impedance, connected in shunt with said first gas discharge tube. likewise receptive of the output oi said rectifying means, and presenting a variable potential, at the junction of said series connection, in response to fluctuations in saidA-C. output; and a vacuum tube having it s"inpu t' connected across the series network including 'said" fired impedance and said first gas discharge tube, whereby the difierence between said variablepotential and said constant voltage drop is applied thereto and amplified thereby.

3. In a circuit for stabilizing the operation of the control means of an A.-C. line regulating system, means for generating D. C. for application to said control means comprising: means for rectifying a portion of the A.=C. output of said systern and applying the resulting D, C. to said control means; a phase-shitting network including a saturable reactor. receptive of another portion of said A.-C. output, for adjusting the phase of said other portion with respect to the input to said rectifying means; means for applying the output of said phase-shifting network to said rectiiying means; and means for applying a D. 0., variable as a function of the magnitude of any fluctuation in said A.-C. output, to said saturable reactor, whereby the impedance thereof is altered 'and'the magnitude'oi the phase shii't introduced by said network is thereby adjusted to control the lit-C. output of said rectifying means.

' :4. In a circuit for stabilizing the operation 01 the control means of an A.-C. line regulating system: means for rectifying a portion of the ARC. output of said system; means for comparing the magnitude of the resulting D. C. with a reference potential established in the system and deriving therefrom a variable D. C. proportional to the difference therebetween; means for amplitying the variable difierence D. C. thus obtained; means for rectifying another portion of the A.-C. output or said system and applying the output thereof to said control means; means, responsive to variations in said variable diii'erence D. C. for

controlling the magnitude of the D.-C. output of said second-named rectifying means; and means, receptive oi a portion or said last named D.-C. output, for applying negative teed-back in said amplifying means, whereby the response of the latter to sudden change in the magnitude of the A.-C. output of the system is sufilciently damped to prevent said system from hunting.

5. In a circuit for stabilizing the operation of a variabie potential, at the junction of said series connection, in response to fluctuations in plifled thereby.

the control means of an A.-C. line regulating sys-- ing the variable diiference D. C. thus obtained;

means for rectifying another portion of the A.-C. output of said system and applying the output thereof to said control means: means, responsive to variations in said variable difference D. C., for controlling the magnitude of the D.-C. output of said second-named rectifying means; and means,

includin'g an R.-C.-network having a time constant which is long compared with the inherent time constant of said system, receptive of a portion of said last-named D.-C. output, for applying negative feed-back to said amplifying means, whereby the response of the latter to sudden change in the magnitude oi the A.-C. output of the system is sufficiently damped to preven said system from hunting.

6. In a circuit for stabilizing the operation of the control means ofan A.-C. line regulating system, means for comparing the magnitude of the A.-C. output of said system with a reference potential established therein, and deriving therefrom a variable D. C. proportional to the difi'erence therebetween, comprising: means for producing a D. C. whose magnitude is proportional to that of said A.-C. output; means, receptive of said D. C., for establishing in said circuit a constant voltage drop; an automatically variable impedance in series with a fixed impedance, connected in shunt with said second-named means, likewise receptive of said D. C., and presenting 7. In a circuit for stabilizing the operation of the control means of an A.-C. line regulating system, means for comparing the magnitude of the A.-C. output oi said system with a reference D0- tential established therein, and deriving therefrom a variable D. C. proportional to the difference therebetween, comprising: means for producing a D. C. whose magnitude is proportional to that of said A.-C. output; an automatically variable impedance, receptive of said D, C., and presenting a constant voltage drop thereacross; a second automatically variable impedance in series with a fixed impedance, connected in shunt with said first automatically variable impedance, likewise receptive of said D. C., and presenting a variable potential, at the junction of said series connection, in response to fluctuations in said A.-C. output; and means connected across the series network including said fixed impedance and said first automatically variable impedance, whereby the difierence between said variable potential and said constant voltage drop is applied thereto and amplified thereby.

PAUL H. ODESSEY.

appearances strap The following references are of record in the tile of this patent:

UNI STATES PATENTS Beeley Feb. 18, 1936 

